How Do I Fix It?
Possible Cause Action
Model cannot initialize to steady
state.- Increase the number of periods for frequencies
that do not reach steady state by changing the
NumPeriods and SettlingPeriods properties.
See “Modify Estimation Input Signals” on page 5-
46. - Disable all time-varying source blocks in your
model and repeat the estimation. See “Effects of
Time-Varying Source Blocks on Frequency
Response Estimation” on page 5-60.
(Sinestream input) Not enough
periods for the output to reach
steady state. - Increase the number of periods for frequencies
that do not reach steady state by changing the
NumPeriods and SettlingPeriods. See
“Modify Estimation Input Signals” on page 5-46. - Check that filtering is enabled during estimation.
You enable filtering by setting the
ApplyFilteringInFRESTIMATE option to on.
For information about how estimation uses
filtering, see the frestimate reference page.
(Chirp input) Signal sweeps
through the frequency range too
quickly.
Increase the simulation time by increasing
NumSamples. See “Modify Estimation Input Signals”
on page 5-46.After you try the suggested actions, recompute the estimation either:
- At all frequencies
- In a particular frequency range (only for sinestream input signals)
To recompute the estimation in a particular frequency range:
1 Determine the frequencies for which you want to recompute the estimation results.
Then, extract a portion of the sinestream input signal at these frequencies using
fselect.
For example, these commands extract a sinestream input signal between 10 and 20
rad/s from the input signal input:input2 = fselect(input,10,20);Troubleshooting Frequency Response Estimation